U.S. patent number 6,915,681 [Application Number 10/397,527] was granted by the patent office on 2005-07-12 for gear-shift control device and gear-shift control method for automatic transmission.
This patent grant is currently assigned to Aisin AW Co., LTD, Toyota Jidosha Kabushiki Kaisha. Invention is credited to Masahiko Ando, Takeshi Gotou, Masato Kaigawa, Yasushi Kobiki, Noritaka Takebayashi.
United States Patent |
6,915,681 |
Kaigawa , et al. |
July 12, 2005 |
Gear-shift control device and gear-shift control method for
automatic transmission
Abstract
An ECT-ECU includes a circuit that calculates an oil temperature
threshold on the basis of a signal input from one of an engine
coolant temperature sensor, an engine intake air temperature
sensor, and an AT hydraulic fluid temperature sensor if a signal
for starting an engine of a vehicle is input thereto from an
ignition switch, a circuit that detects an oil temperature on the
basis of a signal input from the AT hydraulic fluid temperature
sensor at intervals of a predetermined sampling time while the
vehicle is running, and a circuit that controls an automatic
transmission to prohibit a gear shift from fourth speed to fifth
speed if a detected oil temperature is lower than the oil
temperature threshold.
Inventors: |
Kaigawa; Masato (Toyota,
JP), Kobiki; Yasushi (Toyota, JP),
Takebayashi; Noritaka (Toyota, JP), Ando;
Masahiko (Anjo, JP), Gotou; Takeshi (Anjo,
JP) |
Assignee: |
Toyota Jidosha Kabushiki Kaisha
(Toyota, JP)
Aisin AW Co., LTD (Anjo, JP)
|
Family
ID: |
28671674 |
Appl.
No.: |
10/397,527 |
Filed: |
March 27, 2003 |
Foreign Application Priority Data
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Mar 28, 2002 [JP] |
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2002-091044 |
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Current U.S.
Class: |
73/114.68 |
Current CPC
Class: |
F16H
59/72 (20130101); F16H 61/16 (20130101) |
Current International
Class: |
F16H
61/16 (20060101); F16H 59/72 (20060101); G01M
013/02 () |
Field of
Search: |
;73/112,116,117.2,117.3,118.1,119R ;374/141,144 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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64-35153 |
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Feb 1989 |
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JP |
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2-97761 |
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Apr 1990 |
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JP |
|
64-35154 |
|
Feb 1998 |
|
JP |
|
Primary Examiner: McCall; Eric S.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, P.C.
Claims
What is claimed is:
1. A control device for an automatic transmission installed in a
vehicle, comprising: a detecting portion that detects a timing when
an engine of the vehicle is to be started; an oil temperature
detecting portion that detects a temperature of hydraulic fluid
contained in the automatic transmission; a storing portion that
stores a relationship between the temperature of the hydraulic
fluid at engine start and an oil temperature threshold; a
calculating portion that calculates the oil temperature threshold
corresponding to the hydraulic fluid temperature detected by the
oil temperature detecting portion at the timing detected by the
detecting portion on the basis of the relationship stored in the
storing portion; and a control portion that controls the automatic
transmission to prohibit a gear shift to a specific gear stage if
the hydraulic fluid temperature detected by the oil temperature
detecting portion is equal to or lower than the oil temperature
threshold calculated by the calculating portion while the vehicle
is running.
2. The control device according to claim 1, wherein the detecting
portion detects the timing when the engine is to be started on the
basis of operation of an ignition key of the vehicle.
3. The control device according to claim 1, wherein the oil
temperature detecting portion includes two or more sensors for
detecting the temperature of hydraulic fluid contained in the
automatic transmission, a portion for detecting an abnormality of
each of the sensors, and a portion for selecting the hydraulic
fluid temperature detected by one of the sensors that has been
detected to be normal as a hydraulic fluid temperature.
4. The control device according to claim 1, wherein the gear shift
to the specific gear stage is made by engaging a clutch by a direct
pressure in a state where another clutch is engaged.
5. A control method for an automatic transmission installed in a
vehicle, comprising: a detecting step for detecting a timing when
an engine of the vehicle is to be started; an oil temperature
detecting step for detecting a temperature of hydraulic fluid
contained in the automatic transmission; a preparing step for
preparing in advance a relationship between the temperature of the
hydraulic fluid at engine start and an oil temperature threshold; a
calculating step for calculating the oil temperature threshold
corresponding to the hydraulic fluid temperature detected by the
oil temperature detecting step at the timing detected in the
detecting step on the basis of the prepared relationship; and a
control step for controlling the automatic transmission to prohibit
a gear shift to a specific gear stage if the hydraulic fluid
temperature detected in the oil temperature detecting step is equal
to or lower than the oil temperature threshold calculated in the
calculating step while the vehicle is running.
6. The control method according to claim 5, wherein the detecting
step including a step of detecting, on the basis operation of an
ignition key of the vehicle, the timing when the engine is
started.
7. The control method according to claim 5, wherein the oil
temperature detecting step includes a step of detecting abnormality
of two or more sensors for detecting the temperature of hydraulic
fluid contained in the automatic transmission and a step of
selecting the hydraulic fluid temperature detected by one of
sensors that has been detected to be normal as a hydraulic fluid
temperature.
8. The control method according to claim 5, wherein the gear shift
to the specific gear stage is made by engaging a clutch by a direct
pressure in a state where another clutch is engaged.
Description
INCORPORATION BY REFERENCE
The disclosures of Japanese Patent Application No. 2002-091044
filed on Mar. 28, 2002 including the specification, drawings, and
abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a control device for a vehicular automatic
transmission and, more particularly, to a device for controlling an
automatic transmission on the basis of a temperature of hydraulic
fluid contained therein.
2. Description of the Related Art
As an automatic transmission to be installed in a vehicle, there
has generally been employed a transmission that is constructed by
combining a torque converter composed of a pump, a turbine, a
stator, and the like with a multistage-type gear-shift mechanism
connected to the turbine of the torque converter. This automatic
transmission is usually equipped with a hydraulic circuit portion
and a hydraulic control device as a main component. The hydraulic
control device couples and releases hydraulically operated
frictional coupling elements in the gear-shift mechanism such as
clutches and brakes whereby a gear-shift operation of the automatic
transmission is performed. In an automatic transmission equipped
with such a hydraulic control device, when a gear-shift operation
thereof is performed, hydraulic fluid pressure is supplied to a
hydraulic circuit portion for operating frictional coupling
elements. For establishing the hydraulic fluid pressure, an open
period, an opening, or the like of a hydraulic control valve
included in the hydraulic circuit portion is changed in accordance
with a pulse duty factor or the like of a drive pulse signal
supplied from a control unit to the hydraulic control valve. The
hydraulic fluid pressure is thereby controlled. If the frictional
coupling elements abruptly shift from a released state to a coupled
state during control, a gear-shift shock may be caused.
Accordingly, the hydraulic pressure supplied to the frictional
coupling elements is regulated whereby the frictional coupling
elements shift from a released state to a half-coupled state and
then to a coupled state. In this manner, the frictional coupling
elements can be shifted from an engaged state to a coupled state
without causing a gear-shift shock.
As described above, in the case where the hydraulic fluid pressure
supplied to the frictional coupling elements is changed in
accordance with a predetermined characteristic, if the hydraulic
fluid is at a low temperature, the viscosity thereof is higher in
comparison with the case where the hydraulic fluid is at a high
temperature, and a gear-shift operation in the automatic
transmission undergoes a decline in responsiveness. Hence, although
the frictional coupling elements are coupled at a suitable timing
when hydraulic fluid is at a relatively high temperature, hydraulic
fluid is supplied to or discharged from the frictional coupling
elements with delay if the hydraulic fluid reaches a relatively low
temperature. For this reason, there are some cases where the
frictional coupling elements cannot be released or coupled at a
suitable timing. As a result, a gear-shift shock may be caused.
Japanese Patent Application Laid-Open No. 64-35154 discloses a
hydraulic control device for an automatic transmission as a
solution to such a problem. The control device disclosed in this
publication includes frictional engagement elements, a hydraulic
control circuit, an oil temperature detecting circuit, and a
control characteristic changing circuit. The frictional engagement
elements are hydraulically operated and are designed to perform a
gear-shift operation in the automatic transmission. To cause the
frictional engagement elements to perform the gear-shift operation,
the hydraulic control circuit supplies hydraulic fluid in
accordance with a predetermined control characteristic. The oil
temperature detecting circuit detects a hydraulic fluid temperature
that generates a hydraulic fluid pressure. The control
characteristic changing circuit causes the hydraulic control
circuit to change a control characteristic during control of the
supply of hydraulic fluid pressure to the frictional engagement
elements in accordance with a hydraulic fluid temperature detected
by the oil temperature detecting circuit.
According to this control device, the hydraulic fluid pressure
supplied to the frictional engagement elements is changed on the
basis of a control characteristic corresponding to the temperature
of the hydraulic fluid contained in the automatic transmission
Hence, the frictional engagement elements are operated without
delay, for example, when hydraulic fluid is at a low temperature,
and timings for engaging the frictional engagement elements and the
like are suitably controlled.
A sensor for detecting a temperature of the hydraulic fluid
contained in an automatic transmission is usually installed close
to an exit of a torque converter that generates a large amount of
heat and that tends to be a high-temperature area, for example, due
to restrictions imposed on locations where the sensor can be
installed. Hence, the sensor does not directly measure a hydraulic
fluid temperature in the vicinity of an actuator or a valve that
actually performs gear-shift control. Furthermore, since the
hydraulic circuit of the automatic transmission is structurally
complicated, the hydraulic fluid temperature varies widely with
location. Thus, there are some cases where an oil temperature
detected by the sensor is greatly different from a hydraulic fluid
temperature in the vicinity of the actuator or the valve that
actually performs gear-shift control. Especially in a
low-temperature area, the hydraulic circuit itself has cooled.
Therefore, hydraulic fluid is cooled while circulating through the
hydraulic circuit or hydraulic fluid that has cooled continues to
stay where it is. As a result, oil temperatures in the vicinity of
the actuator and the valve as operating regions become lower than
the oil temperature detected by the sensor.
If the control device disclosed in the abovementioned publication
is applied under such a circumstance, gear-shift control cannot be
performed on the basis of oil temperatures in actual operating
regions. Therefore, a gear-shift shock may be caused.
If hydraulic fluid contained in the automatic transmission is at a
low temperature, the viscosity thereof rises. Thus, a deterioration
in responsiveness based on a clutch-to-clutch operation using a
direct pressure is caused. Hence, as a solution different from the
one disclosed in the above-mentioned publication, there is a
control device that performs control in such a manner as to
prohibit a gear shift to a specific gear stage if the hydraulic
fluid temperature falls below a predetermined threshold. In such a
control device as well, since prohibition of a gear shift cannot be
controlled on the basis of an oil temperature in an actual
operating region, the following problem is caused. Even if a
measured oil temperature is high and hydraulic fluid in the
operating region is at a low temperature, the threshold needs to be
set high in advance in order to prohibit a gear shift to a specific
gear stage. In the case where the threshold is thus set, if a
difference between the measured oil temperature and the oil
temperature in the operating region is small. nullification of
prohibition of the gear shift is retarded and a gear shift to a
higher gear stage is made with delay. As a result, driveability and
fuel consumption are adversely affected.
SUMMARY OF THE INVENTION
The invention has been made in response to the problems mentioned
above. It is an object of the invention to provide a gear-shift
control device and a gear-shift control method for controlling a
gear shift in an automatic transmission installed in a vehicle on
the basis of a temperature of hydraulic fluid contained in the
automatic transmission without the necessity to mount a large
number of oil temperature sensors in coordination with the
construction of a hydraulic circuit of the automatic
transmission.
In order to achieve the above-mentioned object, a control device
for an automatic transmission installed in a vehicle as one aspect
of the invention comprises a detecting portion that detects a
timing when an engine of the vehicle is to be started, an oil
temperature detecting portion that detects a temperature of
hydraulic fluid contained in the automatic transmission, a storing
portion that stores an oil temperature threshold corresponding to
the hydraulic fluid temperature at the time when the engine is
started, a calculating portion that calculates an oil temperature
threshold on the basis of an oil temperature detected by the oil
temperature detecting portion at a timing detected by the detecting
portion, and a control portion that controls the automatic
transmission in such a manner as to prohibit a gear shift to a
specific gear stage if the oil temperature detected by the oil
temperature detecting portion is equal to or lower than the oil
temperature threshold calculated by the calculating portion while
the vehicle is running.
A control method corresponding to the control device is designed to
control an automatic transmission installed in a vehicle. This
control method comprises a detecting step for detecting a timing
when an engine of the vehicle is to be started, an oil temperature
detecting step for detecting a temperature of hydraulic fluid
contained in the automatic transmission, a preparing step for
preparing in advance an oil temperature threshold corresponding to
the hydraulic fluid temperature at the time when the engine is
started, a calculating step for calculating an oil temperature
threshold on the basis of an oil temperature detected in the oil
temperature detecting step at a timing detected in the detecting
step, and a control step for controlling the automatic transmission
in such a manner as to prohibit a gear shift to a specific gear
stage if the oil temperature detected in the oil temperature
detecting step is equal to or lower than the oil temperature
threshold calculated in the calculating step while the vehicle is
running.
A control device as another aspect of the invention controls an
automatic transmission installed in a vehicle. This control device
comprises a detecting portion that detects a timing when an engine
of the vehicle is to be started, an oil temperature detecting
portion that detects a temperature of hydraulic fluid contained in
the automatic transmission, a coolant temperature detecting portion
for detecting a coolant temperature for the engine, a storing
portion that stores an oil temperature threshold corresponding to
the hydraulic fluid temperature at the time when the engine is
started, a calculating portion that calculates an oil temperature
threshold on the basis of a coolant temperature detected by the
coolant temperature detecting portion at a timing detected by the
detecting portion, and a control portion that controls the
automatic transmission in such a manner as to prohibit a gear shift
to a specific gear stage if the oil temperature detected by the oil
temperature detecting portion is equal to or lower than the oil
temperature threshold calculated by the calculating portion while
the vehicle is running.
A control method corresponding to the control device comprises a
detecting step for detecting a timing when an engine of the vehicle
is to be started, an oil temperature detecting step for detecting a
temperature of the hydraulic fluid contained in the automatic
transmission, a coolant temperature detecting step for detecting a
coolant temperature for the engine, a preparing step for preparing
in advance an oil temperature threshold corresponding to the
temperature of coolant at the time when the engine is started, a
calculating step for calculating an oil temperature threshold on
the basis of a coolant temperature detected in the coolant
temperature detecting step at a timing detected in the detecting
step, and a control step for controlling the automatic transmission
in such a manner as to prohibit a gear shift to a specific gear
stage if the oil temperature detected in the oil temperature
detecting step is equal to or lower than the oil temperature
threshold calculated in the calculating step while the vehicle is
running.
A control device as another aspect of the invention comprises a
detecting portion for detecting a timing when an engine of the
vehicle is to be started, an oil temperature detecting portion for
detecting a temperature of hydraulic fluid contained in the
automatic transmission, an intake air temperature detecting portion
for detecting a temperature of intake air introduced into the
engine, a storing portion for storing an oil temperature threshold
corresponding to the temperature of intake air at the time when the
engine is started, a calculating portion that calculates an oil
temperature threshold on the basis of the intake air temperature
detected by the intake air temperature detecting portion at a
timing detected by the detecting portion, and a control portion for
controlling the automatic transmission in such a manner as to
prohibit a gear shift to a specific gear stage if the oil
temperature detected by the oil temperature detecting portion is
equal to or lower than the oil temperature threshold calculated by
the calculating portion while the vehicle is running.
A control method corresponding to the control device comprises a
detecting step for detecting a timing when an engine of the vehicle
is to be started, an oil temperature detecting step for detecting a
temperature of hydraulic fluid contained in the automatic
transmission, an intake air temperature detecting step for
detecting a temperature of intake air introduced into the engine, a
preparing step for preparing in advance an oil temperature
threshold corresponding to the temperature of intake air at the
time when the engine is started, a calculating step for calculating
an oil temperature threshold on the basis of the intake air
temperature detected in the coolant temperature detecting step at a
timing detected in the detecting step, and a control step for
controlling the automatic transmission in such a manner as to
prohibit a gear shift to a specific gear stage if the oil
temperature detected in the oil temperature detecting step is equal
to or lower than the oil temperature threshold calculated in the
calculating step while the vehicle is running.
A control device as another aspect of the invention comprises a
detecting portion for detecting a first timing when an engine of
the vehicle is stopped and a second timing which follows the first
timing and at which the engine of the vehicle is started next time,
an oil temperature detecting portion for detecting a temperature of
hydraulic fluid contained in the automatic transmission, a
measuring portion that measures a time that elapses from the first
timing to the second timing, a storing portion for storing an oil
temperature threshold corresponding to the time, a calculating
portion that calculates an oil temperature threshold on the basis
of a time measured by the measuring portion at the second timing
detected by the detecting portion, and a control portion for
controlling the automatic transmission in such a manner as to
prohibit a gear shift to a specific gear stage if the oil
temperature detected by the oil temperature detecting portion is
equal to or lower than the oil temperature threshold calculated by
the calculating portion while the vehicle is running.
A control method corresponding to the control device comprises a
detecting step for detecting a first timing when an engine of the
vehicle is stopped and a second timing which follows the first
timing and at which the engine of the vehicle is started next time,
an oil temperature detecting step for detecting a temperature of
hydraulic fluid contained in the automatic transmission, a
measuring step for measuring a time that elapses from the first
timing to the second timing, a preparing step for preparing in
advance an oil temperature threshold corresponding to the elapsed
time, a calculating step for calculating an oil temperature
threshold on the basis of a time measured in the measuring step at
a second timing detected in the detecting step, and a control step
for controlling the automatic transmission in such a manner as to
prohibit a gear shift to a specific gear stage if the oil
temperature detected in the oil temperature detecting step is equal
to or lower than the oil temperature threshold calculated in the
calculating step while the vehicle is running.
A control device as another aspect of the invention comprises a
detecting portion for detecting a timing when an engine of the
vehicle is to be started, an oil temperature detecting portion for
detecting a temperature of hydraulic fluid contained in the
automatic transmission, a coolant temperature detecting portion for
detecting a coolant temperature for the engine, an intake air
temperature detecting portion for detecting a temperature of intake
air introduced into the engine, a storing portion for storing an
oil temperature threshold corresponding to the hydraulic fluid
temperature at the time when the engine is started, an oil
temperature threshold corresponding to the temperature of coolant
at the time when the engine is started, and an oil temperature
threshold corresponding to the temperature of intake air at the
time when the engine is started, a calculating portion that
calculates an oil temperature threshold on the basis of one of an
oil temperature detected by the oil temperature detecting portion,
a coolant temperature detected by the coolant temperature detecting
portion, and the intake air temperature detected by the intake air
temperature detecting portion at a timing detected by the detecting
portion, and a control portion for controlling the automatic
transmission in such a manner as to prohibit a gear shift to a
specific gear stage if the oil temperature detected by the oil
temperature detecting portion is equal to or lower than the oil
temperature threshold calculated by the calculating portion while
the vehicle is running.
A control method as another aspect of the invention comprises a
detecting step for detecting a timing when an engine of the vehicle
is to be started, an oil temperature detecting step for detecting a
temperature of hydraulic fluid contained in the automatic
transmission, a coolant temperature detecting step for detecting a
coolant temperature for the engine, an intake air temperature
detecting step for detecting a temperature of intake air introduced
into the engine, a preparing step for preparing in advance an oil
temperature threshold corresponding to the hydraulic fluid
temperature at the time when the engine is started, an oil
temperature threshold corresponding to the temperature of coolant
at the time when the engine is started, and an oil temperature
threshold corresponding to the temperature of intake air at the
time when the engine is started, a calculating step for calculating
an oil temperature threshold on the basis of one of an oil
temperature detected in the oil temperature detecting step, a
coolant temperature detected in the coolant temperature detecting
step, and an intake air temperature detected in the intake air
temperature detecting step at a timing detected in the detecting
step, and a control step for controlling the automatic transmission
in such a manner as to prohibit a gear shift to a specific gear
stage if the oil temperature detected in the oil temperature
detecting step is equal to or lower than the oil temperature
threshold calculated in the calculating step while the vehicle is
running.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a control block diagram of a system including an ECT-ECU
that realizes a control device for an automatic transmission in
accordance with embodiments of the invention.
FIG. 2 shows a relationship that is stored in a memory of an
ECT-ECU in accordance with the first embodiment of the invention
and that indicates how the oil temperature threshold is related to
the initial oil temperature.
FIG. 3 is a flowchart showing a control structure of a program that
is executed by the ECT-ECU in accordance with the first embodiment
of the invention.
FIG. 4 shows a relationship that is stored in a memory of an
ECT-ECU in accordance with the second embodiment of the invention
and that indicates how the oil temperature threshold is related to
the initial coolant temperature.
FIG. 5 is a flowchart showing a control structure of a program that
is executed by the ECT-ECU in accordance with the second embodiment
of the invention.
FIG. 6 shows a relationship that is stored in a memory of an
ECT-ECU in accordance with the third embodiment of the invention
and that indicates how the oil temperature threshold is related to
the initial intake air temperature.
FIG. 7 is a flowchart showing a control structure of a program that
is executed by the ECT-ECU in accordance with the third embodiment
of the invention.
FIG. 8 shows a relationship that is stored in a memory of an
ECT-ECU in accordance with the fourth embodiment of the invention
and that indicates how the oil temperature threshold is related to
the engine stop time.
FIG. 9 is a flowchart showing a control structure of a program that
is executed by the ECT-ECU in accordance with the fourth embodiment
of the invention.
FIG. 10 is a flowchart showing a control structure of a program
that is executed by an ECT-ECU in accordance with the fifth
embodiment of the invention.
FIG. 11 is a flowchart showing a control structure of a program
that is executed by an ECT-ECU in accordance with the sixth
embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Hereinafter, the embodiments of the invention will be described
with reference to the drawings. In the following description, like
parts are denoted by like reference symbols and are identical in
name and function as well. Therefore, repetition of detailed
description of those parts will be avoided.
[First Embodiment]
FIG. 1 is a control block diagram of an automatic gear-shift system
including an ECT-ECU (Electronically Controlled Automatic
Transmission--Electronic Control Unit) 100 that realizes a control
device for an automatic transmission in accordance with the first
embodiment. As shown in FIG. 1, the ECT-ECU 100 of this system is a
controller for controlling the automatic transmission. The ECT-ECU
100 includes a memory that stores programs and various data, a CPU
(Central Processing Unit) that executes the programs stored in the
memory, a clock that generates a fundamental motion frequency, and
the like. The ECT-ECU 100 corresponds to a calculating portion as
calculating means, a storing portion as storing means, a control
portion as control means, and a measuring portion as measuring
means.
Input signal lines extending from an ignition switch 200, an engine
coolant temperature sensor 300, an engine intake air temperature
sensor 400, and an AT hydraulic fluid temperature sensor 500 are
connected to the ECT-ECU 100. The ignition switch 200 corresponds
to a detecting portion as detecting means for detecting a timing
when an engine is to be started. The engine coolant temperature
sensor 300 corresponds to a coolant temperature detecting portion
as coolant temperature detecting means for detecting a coolant
temperature for the engine. The engine intake air temperature
sensor 400 corresponds to an intake air temperature detecting
portion as intake air temperature detecting means for detecting a
temperature of intake air introduced into the engine. The AT
hydraulic fluid temperature sensor 500 corresponds to an oil
temperature detecting portion as oil temperature detecting means
for detecting a temperature of hydraulic fluid contained in the
automatic transmission. Output signal lines extending from the
ECT-ECU 100 are connected to an AT on-off solenoid 600 and an AT
linear solenoid 700.
The ECT-ECU 100 in accordance with the first embodiment detects
start of the engine on the basis of a signal input from the
ignition switch 200. Then, the ECT-ECU 100 detects an oil
temperature of the automatic transmission at the time when the
engine is started and stores it in the memory as an initial oil
temperature. The ECT-ECU 100 calculates an oil temperature
threshold on the basis of the initial oil temperature and a
relationship that is stored in the memory and that is established
between initial oil temperature and oil temperature threshold. As
shown in FIG. 2, according to the relationship that is stored in
the memory and that indicates how the oil temperature threshold is
related to the initial oil temperature, the oil temperature
threshold rises in proportion to a fall in the initial oil
temperature and falls in proportion to a rise in the initial oil
temperature. Although the initial oil temperature and the oil
temperature threshold establish a linear relationship in FIG. 2,
other relationships are possible as well.
If a vehicle starts running after calculation of the oil
temperature threshold, the ECT-ECU 100 detects a temperature of
hydraulic fluid contained in the automatic transmission on the
basis of a signal input from the AT hydraulic fluid temperature
sensor 500. In the first embodiment, if the detected oil
temperature is lower than the oil temperature threshold, a gear
shift from fourth speed to fifth speed in the automatic
transmission is prohibited. If the detected oil temperature becomes
equal to or higher than (the oil temperature threshold +.alpha.),
prohibition of the gear shift from fourth speed to fifth speed is
nullified. It is to be noted herein that the automatic transmission
of the first embodiment is realized as a five-speed automatic
transmission in which a gear shift from fourth speed to fifth speed
is made by a clutch-to-clutch operation based on a direct pressure.
During this gear shift, if a deterioration in responsiveness is
caused due to a low temperature of hydraulic fluid contained in the
automatic transmission, a significant gear-shift shock tends to
occur.
In the case where a gear shift to fifth speed is prohibited, the
ECT-ECU 100 creates a fifth speed prohibition command and sets a
fifth-speed prohibition flag to "on". Even if other fifth-speed
gear-shift conditions are satisfied, the ECT-ECU 100 does not
output a fifth-speed gear-shift indication signal to the AT on/off
solenoid 600 or the AT linear solenoid 700 as long as the
fifth-speed prohibition command has been created.
A control structure of a program that is executed by the ECT-ECU
100 in accordance with the first embodiment will be described with
reference to FIG. 3.
In step (hereinafter simplified as "S") 100, the ECT-ECU 100
determines whether or not the ignition switch has been turned on.
This determination is made on the basis of an input signal that is
input from the ignition switch 200 to the ECT-ECU 100. If the
ignition switch has been turned on (YES in S100), the operation is
shifted to S102. If the ignition switch has not been turned on (NO
in S100), the operation is returned to S100.
In S102, the ECT-ECU 100 detects an AT hydraulic fluid temperature
on the basis of a signal input from the AT hydraulic fluid
temperature sensor 500 and stores it in the memory as an initial
oil temperature. In S104, the ECT-ECU 100 calculates an oil
temperature threshold on the basis of the stored initial oil
temperature. At this moment, the oil temperature threshold is
calculated on the basis of the detected initial oil temperature and
a relationship that is stored in the memory and that indicates how
the oil temperature threshold is related to the initial oil
temperature (FIG. 2).
In S110, the ECT-ECU 100 determines whether or not a sampling time
has been reached. This determination is made on the basis of an
output signal from the clock that is built into the ECT-ECU 100. If
the sampling time has been reached (YES in S110), the operation is
shifted to S112. If the sampling time has not been reached (NO in
S110), the operation is returned to S110.
In S112, the ECT-ECU 100 detects an AT hydraulic fluid temperature
on the basis of a signal input from the AT hydraulic fluid
temperature sensor 500 and stores it in the memory as a current oil
temperature. In S114, the ECT-ECU 100 determines whether or not the
fifth-speed prohibition flag has been set to "on". If the
fifth-speed prohibition flag has been set to "on " (YES in S114),
the operation is shifted to S120. If the fifth-speed prohibition
flag has not been set to "on" (NO in S114), the operation is
shifted to S116.
In S116, the ECT-ECU 100 determines whether or not the current oil
temperature stored in the memory is lower than the oil temperature
threshold. If the current oil temperature is lower than the oil
temperature threshold (YES in S116), the operation is shifted to
S118. If the current oil temperature is not lower than the oil
temperature threshold (NO in S116), the operation is returned to
S110.
In S118, the ECT-ECU 100 creates a fifth-speed prohibition command
and sets the fifth-speed prohibition flag to "on". The operation is
thereafter returned to S110.
In S120, the ECT-ECU 100 determines whether or not the current oil
temperature stored in the memory is equal to or higher than (the
oil temperature threshold +.alpha.). It is to be noted herein that
a is a positive constant. If the current oil temperature is equal
to or higher than (the oil temperature threshold +.alpha.) (YES-in
S120), the operation is shifted to S122. If the current oil
temperature is lower than (the oil temperature threshold +.alpha.)
(NO in S120), the operation is returned to S110.
In S122, the ECT-ECU 100 creates a fifth-speed permission command
and sets the fifth-speed prohibition flag off. The operation is
thereafter returned to S110.
Operation of the ECT-ECU 100 that is based on the structure and the
flowchart as mentioned above and that realizes the control device
for the automatic transmission in accordance with the first
embodiment will be described.
If a user of the vehicle turns the ignition switch on (YES in
S100), the ECT-ECU 100 detects an AT hydraulic fluid temperature on
the basis of a signal input from the AT hydraulic fluid temperature
sensor 500 and stores it in the memory as an initial oil
temperature (S102). An oil temperature threshold is calculated on
the basis of the detected initial oil temperature and the
relationship indicating how the oil temperature threshold is
related to the initial oil temperature (S104).
If the sampling time has been reached after takeoff of the vehicle
(YES in S110), the ECT-ECU 100 detects an AT hydraulic fluid
temperature on the basis of a signal input from the AT hydraulic
fluid temperature sensor 500 and stores it in the memory as a
current oil temperature (S112). If the fifth-speed flag is not on
(No in S114) and if the current oil temperature is lower than the
oil temperature threshold that has been calculated on the basis of
the initial oil temperature (YES in S116), a fifth-speed
prohibition command is created and the fifth-speed prohibition flag
is set to "on" (S118).
If the temperature of hydraulic fluid contained in the automatic
transmission rises because the vehicle has continuously run, the
fifth-speed prohibition flag is on (YES in S114). In this state, if
the current oil temperature becomes equal to or higher than (the
oil temperature threshold +.alpha.) (YES in S120), a fifth-speed
permission command is created and the fifth-speed prohibition flag
is set to "off" (S122).
Thus, according to the control device for the automatic
transmission in accordance with the first embodiment, an oil
temperature threshold is calculated on the basis of a temperature
of hydraulic fluid contained in the automatic transmission at the
time when the engine is started, and fifth-speed prohibition
control is performed on the basis of the oil temperature
threshold.
In the case where the operation as described above is performed,
the oil temperature threshold is a threshold that has been
calculated on the basis of an initial oil temperature at the time
when the engine is started. As shown in FIG. 2, the threshold is
set such that the oil temperature threshold rises in proportion to
a fall in the oil temperature (initial oil temperature) at the time
when the engine is started and the oil temperature threshold falls
in proportion to a rise in initial oil temperature. If the
hydraulic fluid contained in the automatic transmission is
determined to be at a low temperature as a result of the detection
carried out during the start of the engine, the automatic
transmission itself and hydraulic fluid contained therein have
cooled. Thus, even if the oil temperature detected by the AT
hydraulic fluid temperature sensor 500 is high, it is quite likely
that a temperature in the vicinity of a clutch for making a gear
shift from fourth speed to fifth speed should not have risen
sufficiently. Therefore, the oil temperature threshold for
prohibiting a gear shift to fifth speed is set high. On the other
hand, if hydraulic fluid contained in the automatic transmission is
determined to be at a high temperature as a result of the detection
carried out during the start of the engine, the automatic
transmission itself and hydraulic fluid contained therein have been
warmed. Thus, even if the oil temperature detected by the AT
hydraulic fluid temperature sensor 500 is more or less low, it is
quite likely that a temperature in the vicinity of the clutch for
making a gear shift from fourth speed to fifth speed should have
risen. Therefore, the oil temperature threshold for prohibiting a
gear shift to fifth speed is set low.
As described above, according to the control device for the
automatic transmission in accordance with the first embodiment, a
gear shift from fourth speed to fifth speed in the automatic
transmission is made by a clutch-to-clutch operation using direct
pressure. Thus, if hydraulic fluid in the vicinity of the clutch is
at a low temperature, an undesirable lack of responsiveness is
obtained and a gear-shift shock is caused. The oil temperature
detecting portion as the oil temperature detecting means is
installed, for example, at a position that is close to a torque
converter of the automatic transmission and that is different from
regions in the vicinity of the clutch. If hydraulic fluid contained
in the automatic transmission is determined to be at a low
temperature as a result of the detection carried out by the oil
temperature detecting portion in the oil temperature detecting step
during the start of the engine, the automatic transmission itself
and hydraulic fluid contained therein have cooled, for example,
because the vehicle has been stopped for a long time. Thus, even if
the oil temperature detected by the oil temperature detecting
portion in the oil temperature detecting step is high, it is quite
likely that a temperature in the vicinity of the clutch should not
have risen sufficiently. Therefore, the oil temperature threshold
for prohibiting a gear shift to a specific gear stage is set high.
If hydraulic fluid contained in the automatic transmission is
determined to be at a high temperature as a result of the detection
carried out during the start of the engine, the automatic
transmission itself and hydraulic fluid contained therein have been
warmed, for example, because the vehicle has been stopped for a
short period. Thus, even if the oil temperature detected by the oil
temperature detecting portion in the oil temperature detecting step
is more or less low, it is quite likely that a temperature in the
vicinity of the clutch should have risen. Therefore, the oil
temperature threshold for prohibiting a gear shift to a specific
gear stage is set low. Because the oil temperature threshold has
thus been set, it is possible to precisely calculate an oil
temperature threshold for prohibiting a gear shift to a specific
gear stage even in the case where it is impossible to precisely
measure an oil temperature in the vicinity of a frictional coupling
element of the automatic transmission due to a complicated
structure. As a result, there is no need to mount a large number of
oil temperature sensors in coordination with the construction of a
hydraulic circuit of the automatic transmission, and gear shifts in
the automatic transmission can be controlled on the basis of a
temperature of hydraulic fluid contained in the automatic
transmission that is mounted in the vehicle.
According to the above-mentioned construction, a timing for
starting the engine can be detected on the basis of an operation
that is performed by the user to turn the ignition switch on or
off.
Further, according to the above-mentioned construction, a gear
shift to a specific gear stage which is based on a clutch-to-clutch
operation and which is made to switch the clutch to be engaged from
one to another using a direct clutch is greatly influenced by a
deterioration in responsiveness resulting from a fall in
temperature of the hydraulic fluid contained in the automatic
transmission and tends to cause a gear-shift shock. Hence, the gear
shift to the specific gear stage is prohibited until a detected oil
temperature exceeds an oil temperature threshold that has been
calculated on the basis of a hydraulic fluid temperature, an engine
coolant temperature, an engine intake air temperature, an engine
stop time, and the like, at the time when the engine is started. As
a result, it is possible to realize a control device and a control
method which can inhibit the occurrence of a gear-shift shock.
[Second Embodiment]
The ECT-ECU 100 in accordance with the second embodiment detects a
time when the engine is started on the basis of a signal input from
the ignition switch 200, detects an engine coolant temperature at
that moment, and stores it in the memory as an initial coolant
temperature. The ECT-ECU 100 calculates an oil temperature
threshold on the basis of the initial coolant temperature and a
relationship that is stored in the memory and that indicates how
the oil temperature threshold is related to initial coolant
temperature. As shown in FIG. 4, according to the relationship that
is stored in the memory and that indicates how oil temperature
threshold is related to the initial coolant temperature, the oil
temperature threshold rises in proportion to a fall in the initial
coolant temperature and falls in proportion to a rise in the
initial coolant temperature. Although the initial coolant
temperature and oil temperature threshold establish a linear
relationship in FIG. 4, other relationships are possible as well.
Also, the system of the automatic transmission in accordance with
the second embodiment is identical in construction to the system in
accordance with the above-mentioned first embodiment. Accordingly,
detailed description thereof will not be repeated hereinafter.
A control structure of a program executed by the ECT-ECU 100 that
realizes the control device for the automatic transmission in
accordance with the second embodiment will be described with
reference to FIG. 5. In the flowchart shown in FIG. 5, flow
sequences identical to those in the above-mentioned flowchart shown
in FIG. 3 are denoted by the same step numbers. Accordingly, a
detailed description thereof will not be repeated hereinafter.
In S202, the ECT-ECU 100 detects an engine coolant temperature on
the basis of a signal input from the engine coolant temperature
sensor 300 and stores it in the memory as an initial coolant
temperature. In S204, the ECT-ECU 100 calculates an oil temperature
threshold on the basis of the initial coolant temperature stored in
the memory. At this moment, the oil temperature threshold is
calculated on the basis of the detected initial coolant temperature
and a relationship indicating how the oil temperature threshold is
related to the initial coolant temperature (FIG. 4). The flow
sequences in S110 to S112 are thereafter performed repeatedly at
intervals of a sampling time.
Operation of the ECT-ECU 100 that is based on the structure and the
flowchart as mentioned above and that realizes the control device
for the automatic transmission in accordance with the second
embodiment will be described.
If a user of the vehicle turns the ignition switch on (YES in
S100), the ECT-ECU 100 detects an engine coolant temperature on the
basis of a signal input from the engine coolant temperature sensor
300 and stores it in the memory as an initial coolant temperature
(S200). An oil temperature threshold is calculated on the basis of
the detected initial coolant temperature and the relationship
indicating how the oil temperature threshold is related to the
initial coolant temperature (S204). In the case where the sampling
time is reached while the vehicle is running (YES in S110), if a
current oil temperature detected on the basis of a signal input
from the AT hydraulic fluid temperature sensor 500 is lower than
the oil temperature threshold calculated on the basis of the
initial coolant temperature (YES in S116), a fifth-speed
prohibition command is created and the fifth-speed prohibition flag
is set to "Son" (S118).
If the temperature of hydraulic fluid contained in the automatic
transmission rises because the vehicle has continuously run, the
current oil temperature becomes equal to or higher than (the oil
temperature threshold +.alpha.) (YES in S120), a fifth-speed
permission command is created, and the fifth-speed prohibition flag
is set to "off" (S122).
Thus, according to the control device for the automatic
transmission in accordance with the second embodiment, an oil
temperature threshold is calculated on the basis of an engine
coolant temperature at the time when the engine is started, and
fifth-speed prohibition control is performed on the basis of the
oil temperature threshold.
In the case where the operation as described above is performed,
the oil temperature threshold is a threshold that has been
calculated on the basis of an initial coolant temperature at the
time when the engine is started. If engine coolant is determined to
be at a low temperature as a result of the detection carried out
during the start of the engine, the automatic transmission itself
and hydraulic fluid contained therein have cooled because the
vehicle has been stopped for a long time. Thus, even if the oil
temperature detected by the AT hydraulic fluid temperature sensor
is high, it is quite likely that a temperature in the vicinity of a
clutch that is used in making a gear shift from fourth speed to
fifth speed should not have risen sufficiently. Therefore, the oil
temperature threshold for prohibiting a gear shift from fourth
speed to fifth speed is set high. On the other hand, if engine
coolant is determined to be at a high temperature as a result of
the detection carried out during the start of the engine, the
automatic transmission itself and hydraulic fluid contained therein
have been warmed because the vehicle has been stopped for a short
time. Thus, even if the oil temperature detected by the AT
hydraulic fluid temperature sensor is more or less low, it is quite
likely that a temperature in the vicinity of the clutch that is
used in making a gear shift from fourth speed to fifth speed should
have risen. Therefore, the oil temperature threshold for
prohibiting a gear shift from fourth speed to fifth speed is set
low.
As described above, according to the control device and the control
method for the automatic transmission in accordance with the second
embodiment, if the engine coolant is determined to be at a low
temperature as a result of the detection carried out during the
start of the engine, the automatic transmission itself and the
hydraulic fluid contained therein have cooled, for example, because
the vehicle has been stopped for a long time. Thus, even if the oil
temperature detected by the oil temperature detecting portion in
the oil temperature detecting step is high, it is quite likely that
a temperature in the vicinity of the clutch should not have risen
sufficiently. Therefore, the oil temperature threshold for
prohibiting a gear shift to a specific gear stage is set high. If
the engine coolant is determined to be at a high temperature as a
result of the detection carried out during the start of the engine,
the automatic transmission itself and hydraulic fluid contained
therein have been warmed, for example, because the vehicle has been
stopped for a short time. Thus, even if the oil temperature
detected by the oil temperature detecting portion is more or less
low, it is quite likely that a temperature in the vicinity of the
clutch should have risen. Therefore, the oil temperature threshold
for prohibiting a gear shift to a specific gear stage is set low.
According to the above-mentioned construction, even if it is
impossible to precisely measure an oil temperature in the vicinity
of a frictional coupling element of the automatic transmission due
to a complicated structure, it is possible to calculate an oil
temperature threshold for prohibiting a gear shift to a specific
gear stage (e.g., a gear shift from fourth speed to fifth speed in
the case of a five-speed automatic transmission) on the basis of an
engine coolant temperature at the time when the engine is started.
As a result, it is possible to provide a gear-shift control device
and a gear-shift control method for controlling a gear shift in an
automatic transmission installed in a vehicle on the basis of a
temperature of hydraulic fluid contained in the automatic
transmission without the necessity of mounting a large number of
oil temperature sensors in coordination with the construction of a
hydraulic circuit of the automatic transmission. Because the oil
temperature threshold has thus been set, it is possible to
precisely calculate an oil temperature threshold for prohibiting a
gear shift to a specific gear stage even in the case where it is
impossible to precisely measure an oil temperature in the vicinity
of a frictional coupling element of the automatic transmission due
to a complicated structure.
[Third Embodiment]
The ECT-ECU 100 in accordance with the third embodiment detects
start of the engine on the basis of a signal input from the
ignition switch 200, detects a temperature of intake air introduced
into the engine at that moment, and stores it in the memory as an
initial intake air temperature. The ECT-ECU 100 calculates an oil
temperature threshold on the basis of the initial intake air
temperature and a relationship that is stored in the memory and
that indicates how the oil temperature threshold is related to the
initial intake air temperature. As shown in FIG. 6, according to
the relationship that is stored in the memory and that indicates
how the oil temperature threshold is related to the initial intake
air temperature, the oil temperature threshold rises in proportion
to a fall in the initial intake air temperature and falls in
proportion to a rise in the initial intake air temperature.
Although the initial intake air temperature and oil temperature
threshold establish a linear relationship in FIG. 6, other
relationships are possible as well. Also, the system of the
automatic transmission in accordance with the third embodiment is
identical in construction to the system in accordance with the
above-mentioned first embodiment. Accordingly, a detailed
description thereof will not be repeated hereinafter.
A control structure of a program executed by the ECT-ECU 100 that
realizes the control device for the automatic transmission in
accordance with the third embodiment will be described with
reference to FIG. 7. In the flowchart shown in FIG. 7, flow
sequences identical to those in the above-mentioned flowchart shown
in FIG. 3 are denoted by the same step numbers. Accordingly,
detailed description thereof will not be repeated hereinafter.
In S302, the ECT-ECU 100 detects an engine intake air temperature
on the basis of a signal input from the engine intake air
temperature sensor 400 and stores it in the memory as an initial
intake air temperature. In S304, the ECT-ECU 100 calculates an oil
temperature threshold on the basis of the initial intake air
temperature stored in the memory. At this moment, the oil
temperature threshold is calculated on the basis of the detected
initial intake air temperature and a relationship indicating how
the oil temperature threshold is related to the initial intake air
temperature. The flow sequences in S110 to S112 are thereafter
performed repeatedly at intervals of a sampling time.
Operation of the ECT-ECU 100 that is based on the structure and the
flowchart as mentioned above and that realizes the control device
for the automatic transmission in accordance with the third
embodiment will be described.
If a user of the vehicle turns the ignition switch on (YES in
S100), the ECT-ECU 100 detects an engine intake air temperature on
the basis of a signal input from the engine intake air temperature
sensor 400 and stores it in the memory as an initial intake air
temperature (S302). An oil temperature threshold is calculated on
the basis of the initial intake air temperature stored in the
memory and the relationship indicating how the oil temperature
threshold is related to the initial intake air temperature
(S304).
In the case where the sampling time is reached while the vehicle is
running (YES in S110), the ECT-ECU 100 detects a temperature of AT
hydraulic fluid on the basis of a signal input from the AT
hydraulic fluid temperature sensor 500 and stores it in the memory
as a current oil temperature (S112). If the fifth-speed prohibition
flag is not on (NO in S114) and if a current oil temperature is
lower than the oil temperature threshold calculated on the basis of
the initial intake air temperature (YES in S116), a fifth-speed
prohibition command is created and the fifth-speed prohibition flag
is set to "on" (S118).
If the temperature of hydraulic fluid contained in the automatic
transmission rises because the vehicle has continuously run, the
current oil temperature becomes equal to or higher than (the oil
temperature threshold +.alpha.) (YES in S120), a fifth-speed
permission command is created, and the fifth-speed prohibition flag
is set to "off" (S122).
Thus, according to the control device for the automatic
transmission in accordance with the third embodiment, an oil
temperature threshold is calculated on the basis of a temperature
of intake air introduced into the engine at the time when the
engine is started, and fifth-speed prohibition control is performed
on the basis of the oil temperature threshold.
In the case where the operation as described above is performed,
the oil temperature threshold is a threshold that has been
calculated on the basis of an initial intake air temperature at the
time when the engine is started. As shown in FIG. 6, if intake air
introduced into the engine is determined to be at a low temperature
as a result of the detection carried out during the start of the
engine, the automatic transmission itself and hydraulic fluid
contained therein are unlikely to be warm because the atmosphere
surrounding the vehicle has a low temperature. Thus, even if the
oil temperature detected by the AT hydraulic fluid temperature
sensor is high, it is quite likely that a temperature in the
vicinity of a clutch that is used in making a gear shift from
fourth speed to fifth speed should not have risen sufficiently.
Therefore, the oil temperature threshold for prohibiting a gear
shift from fourth speed to fifth speed is set high. On the other
hand, if intake air introduced into the engine is determined to be
at a high temperature as a result of the detection carried out
during the start of the engine, the automatic transmission itself
and hydraulic fluid contained therein are likely to be warm because
the atmosphere surrounding the vehicle has a high temperature.
Thus, even if the oil temperature detected by the AT hydraulic
fluid temperature sensor is more or less low, it is quite likely
that a temperature in the vicinity of the clutch that is used in
making a gear shift from fourth speed to fifth speed should have
risen. Therefore, the oil temperature threshold for prohibiting a
gear shift from fourth speed to fifth speed is set low.
As described above, according to the control device and the control
method for the automatic transmission in accordance with the third
embodiment, if intake air introduced into the engine is determined
to be at a low temperature as a result of the detection carried out
during the start of the engine, hydraulic fluid contained in the
automatic transmission is unlikely to be warm, for example, because
the atmosphere surrounding the vehicle is at a low temperature.
Thus, even if the oil temperature detected by the oil temperature
detecting portion in the oil temperature detecting step is high, it
is quite likely that a temperature in the vicinity of the clutch
should not have risen sufficiently. Therefore, the oil temperature
threshold for prohibiting a gear shift to a specific gear stage is
set high. If intake air introduced into the engine is determined to
be at a high temperature as a result of the detection carried out
during the start of the engine, hydraulic fluid contained in the
automatic transmission is likely to be warm, for example, because
the atmosphere surrounding the vehicle is at a high temperature.
Thus, even if the oil temperature detected by the oil temperature
detecting portion is more or less low, it is quite likely that a
temperature in the vicinity of the clutch should have risen.
Therefore, the oil temperature threshold for prohibiting a gear
shift to a specific gear stage is set low. According to the
above-mentioned construction, even if it is impossible to precisely
measure an oil temperature in the vicinity of a frictional coupling
element of the automatic transmission due to a complicated
structure, it is possible to calculate an oil temperature threshold
for prohibiting a gear shift from fourth speed to fifth speed on
the basis of a temperature of intake air introduced into the engine
at the time when the engine is started. As a result, there is no
need to mount a large number of oil temperature sensors in
coordination with the construction of a hydraulic circuit of the
automatic transmission, and it is possible to control a gear shift
in an automatic transmission installed in a vehicle on the basis of
a temperature of hydraulic fluid contained in the automatic
transmission. Hence, it is possible to precisely calculate an oil
temperature threshold for prohibiting a gear shift to a specific
gear stage even in the case where it is impossible to precisely
measure an oil temperature in the vicinity of a frictional coupling
element of the automatic transmission due to a complicated
structure.
[Fourth Embodiment]
The ECT-ECU 100 in accordance with the fourth embodiment detects
the start of the engine on the basis of a signal input from the
ignition switch 200, detects a time that elapses from a timing when
the engine is stopped the last time to a timing when the engine is
started this time, and stores it into the memory as an engine stop
time. The ECT-ECU 100 calculates an oil temperature threshold on
the basis of the engine stop time and a relationship that is stored
in the memory and that is established between the engine stop time
and the oil temperature threshold. As shown in FIG. 8, according to
the relationship that is stored in the memory and that indicates
how the oil temperature threshold is related to the engine stop
time, the oil temperature threshold rises in proportion to a
decrease in the engine stop time and falls in proportion to an
increase in the engine stop time. Although the engine stop time and
oil temperature threshold establish a linear relationship in FIG.
8, other relationships are possible as well. Also, the system of
the automatic transmission in accordance with the fourth embodiment
is identical in construction to the system in accordance with the
above-mentioned first embodiment. Accordingly, a detailed
description thereof will not be repeated hereinafter.
A control structure of a program executed by the ECT-ECU 100 that
realizes the control device for the automatic transmission in
accordance with the fourth embodiment will be described with
reference to FIG. 9. In the flowchart shown in FIG. 9, flow
sequences identical to those in the above-mentioned flowchart shown
in FIG. 3 are denoted by the same step numbers. Accordingly, a
detailed description thereof will not be repeated hereinafter.
In S402, the ECT-ECU 100 detects a time that elapses from a timing
when the ignition switch is turned off the last time to a timing
when the ignition switch is turned on this time, and stores it in
the memory as an engine stop time. In S404, the ECT-ECU 100
calculates an oil temperature threshold on the basis of the engine
stop time stored in the memory. At this moment, the oil temperature
threshold is calculated on the basis of the detected engine stop
time and a relationship indicating how the oil temperature
threshold is related to the engine stop time (FIG. 8). The
processings in S110 to S112 are thereafter performed repeatedly at
intervals of a sampling time.
Operation of the ECT-ECU 100 that is based on the structure and the
flowchart as mentioned above and that realizes the control device
for the automatic transmission in accordance with the fourth
embodiment will be described.
If a user of the vehicle turns the ignition switch on (YES in
S100), the ECT-ECU 100 detects a time that elapses from a timing
when the ignition switch is turned off last time to a timing when
the ignition switch is turned on this time, and stores it in the
memory as an engine stop time (S402). The ECT-ECU 100 calculates an
oil temperature threshold on the basis of the calculated engine
stop time. At this moment, the oil temperature threshold is
calculated on the basis of the calculated engine stop time and the
relationship indicating how the oil temperature threshold is
related to the engine stop time.
If the sampling time has been reached after takeoff of the vehicle
(YES in S100), the ECT-ECU 100 detects an AT hydraulic fluid
temperature on the basis of a signal input from the AT hydraulic
fluid temperature sensor 500 and stores it in the memory as a
current oil temperature (S112). If the fifth-speed flag is not on
(No in S114) and if the current oil temperature is lower than the
oil temperature threshold that has been calculated on the basis of
the engine stop time (YES in S116), a fifth-speed prohibition
command is created and the fifth-speed prohibition flag is set to
"on" (S118).
If the temperature of hydraulic fluid contained in the automatic
transmission rises because the vehicle has continuously run, the
current oil temperature becomes equal to or higher than (the oil
temperature threshold +.alpha.) (YES in S120), a fifth-speed
permission command is created, and the fifth-speed prohibition flag
is set to "off" (S122).
Thus, according to the control device for the automatic
transmission in accordance with the fourth embodiment, an oil
temperature threshold is calculated on the basis of an engine stop
time, and fifth-speed prohibition control is performed on the basis
of the oil temperature threshold.
In the case where the operation as described above is performed,
the oil temperature threshold is a threshold that has been
calculated on the basis of an engine stop time at the time when the
engine is started. As shown in FIG. 8, if a time that elapses from
a timing when the engine is stopped last time to a timing when the
engine is started this time is determined to be long as a result of
the detection carried out during the start of the engine, the
automatic transmission itself and hydraulic fluid contained therein
have cooled and are unlikely to be warmed. Thus, even if the oil
temperature detected by the AT hydraulic fluid temperature sensor
is high, it is quite likely that a temperature in the vicinity of a
clutch that is used in making a gear shift from fourth speed to
fifth speed should not have risen sufficiently. Therefore, the oil
temperature threshold for prohibiting a gear shift from fourth
speed to fifth speed is set high. On the other hand, if a time that
elapses from a timing when the engine is stopped last time to a
timing when the engine is started this time is determined to be
short as a result of the detection carried out during the start of
the engine, the automatic transmission itself and hydraulic fluid
contained therein are likely to be warm. Thus, even if the oil
temperature detected by the AT hydraulic fluid temperature sensor
is more or less low, it is quite likely that a temperature in the
vicinity of the clutch that is used in making a gear shift from
fourth speed to fifth speed should have risen. Therefore, the oil
temperature threshold for prohibiting a gear shift from fourth
speed to fifth speed is set low.
As described above, according to the control device and the control
method for the automatic transmission in accordance with the fourth
embodiment, if a time that elapses from a timing when the engine is
stopped last time to a timing when the engine is started this time
is determined to be long as a result of the detection carried out
during the start of the engine, the automatic transmission itself
and hydraulic fluid contained therein have cooled and are unlikely
to be warm. Thus, even if the oil temperature detected by the oil
temperature detecting portion in the oil temperature detecting step
is high, it is quite likely that a hydraulic fluid temperature in
the vicinity of the clutch should not have risen sufficiently.
Therefore, the oil temperature threshold for prohibiting a gear
shift to a specific gear stage is set high. If a time that elapses
from a timing when the engine is stopped last time to a timing when
the engine is started this time is determined to be short as a
result of the detection carried out during the start of the engine,
the automatic transmission itself and hydraulic fluid contained
therein are likely to be warm. Thus, even if the oil temperature
detected by the oil temperature detecting portion in the oil
temperature detecting step is more or less low, it is quite likely
that a temperature in the vicinity of the clutch should have risen.
Therefore, the oil temperature threshold for prohibiting a gear
shift to a specific gear stage is set low. According to the
above-mentioned construction, even if it is impossible to precisely
measure an oil temperature in the vicinity of a frictional coupling
element of the automatic transmission due to a complicated
structure, it is possible to calculate an oil temperature threshold
for prohibiting a gear shift from fourth speed to fifth speed on
the basis of an engine stop time at the time when the engine is
started. As a result, there is no need to mount a large number of
oil temperature sensors in coordination with the construction of a
hydraulic circuit of the automatic transmission, and it is possible
to control a gear shift in an automatic transmission installed in a
vehicle on the basis of a temperature of hydraulic fluid contained
in the automatic transmission. Because the oil temperature
threshold has thus been set, it is possible to precisely calculate
an oil temperature threshold for prohibiting a gear shift to a
specific gear stage even in the case where it is impossible to
precisely measure an oil temperature in the vicinity of a
frictional coupling element of the automatic transmission due to a
complicated structure.
[Fifth Embodiment]
The ECT-ECU 100 in accordance with the fifth embodiment detects the
start of the engine on the basis of a signal input from the
ignition switch 200, and calculates an oil temperature threshold on
the basis of one of a temperature of the hydraulic fluid contained
in the automatic transmission (initial oil temperature), an engine
coolant temperature (initial coolant temperature), and a
temperature of intake air introduced into the engine (initial
intake air temperature) and one of a relationship that is stored in
the memory and that indicates how the oil temperature threshold is
related to the initial oil temperature, a relationship that is
stored in the memory and that indicates how the oil temperature
threshold is related to the initial coolant temperature, and a
relationship that is stored in the memory and that indicates how
the oil temperature threshold is related to the initial intake air
temperature.
The ECUT-ECU 100 respectively determines, on the basis of signals
input from the engine coolant temperature sensor 300, the engine
intake air temperature sensor 400, and the AT hydraulic fluid
temperature sensor 500, whether or not these sensors are abnormal.
For example, if the signal input to the ECT-ECU 100 from a certain
one of the sensors is out of a measurable range, it is determined
that the signal line extending from that sensor has been
short-circuited or broken. If the signal input to the ECT-ECU 100
from a certain one of the sensors is within the measurable range
but remains unchanged for a long time, it is also determined that
that sensor is abnormal. The ECT-ECU 100 selects a normal one of
the sensors on the basis of this determination, and calculates an
oil temperature threshold on the basis of one of a temperature of
hydraulic fluid contained in the automatic transmission (initial
oil temperature), an engine coolant temperature (initial coolant
temperature), and a temperature of intake air introduced into the
engine (initial intake air temperature).
The system of the automatic transmission in accordance with the
fifth embodiment is identical in construction to the system in
accordance with the above-mentioned first embodiment. Accordingly,
a detailed description thereof will not be repeated
hereinafter.
A control structure of a program executed by the ECT-ECU 100 that
realizes the control device for the automatic transmission in
accordance with the fifth embodiment will be described with
reference to FIG. 10. In the flowchart shown in FIG. 10, flow
sequences identical to those in the above-mentioned flowchart shown
in FIG. 3 are denoted by the same step numbers. Accordingly,
detailed description thereof will not be repeated hereinafter.
In S502, on the basis of signals input from the engine coolant
temperature sensor 300 and the engine intake air temperature
sensor.400, the ECT-ECU 100 makes determination concerning an
abnormal state of each of the sensors. At this moment, if the
signal input from a certain one of the sensors is out of a
predetermined measurable range, it is determined that that sensor
is abnormal. Alternatively, if the signal input from a certain one
of the sensors remains unchanged for a predetermined time, an
abnormal state of that sensor is detected.
In S504, the ECT-ECU 100 determines whether or not the engine
coolant temperature sensor 300 is abnormal. If the engine coolant
temperature sensor 300 is abnormal (YES in S504), the operation is
shifted to S506. If the engine coolant temperature sensor 300 is
not abnormal (NO in S504), the operation is shifted to S508.
In S506, the ECT-ECU 100 determines whether or not the engine
intake air temperature sensor 400 is abnormal. If the engine intake
temperature sensor 400 is abnormal (YES in S506), the operation is
shifted to S516. If the engine intake temperature sensor 400 is not
abnormal (NO in S506), the operation is shifted to S512.
In S508, the ECT-ECU 100 detects an engine coolant temperature and
stores it in the memory as an initial coolant temperature. In S510,
the ECT-ECU 100 calculates an oil temperature threshold on the
basis of the initial coolant temperature. At this moment, the
relationship indicating how the oil temperature threshold is
related to the initial coolant temperature (FIG. 4) is used.
In S512, the ECT-ECU 100 detects an engine intake air temperature
and stores it in the memory as an initial intake air temperature.
In S514, the ECT-ECU 100 calculates an oil temperature threshold on
the basis of the initial intake air temperature. At this moment,
the relationship indicating how the oil temperature threshold is
related to the initial intake air temperature (FIG. 6) is used.
In S516, the ECT-ECU 100 detects an AT hydraulic fluid temperature
and stores it in the memory as an initial oil temperature. In S518,
the ECT-ECU 100 calculates an oil temperature threshold on the
basis of the initial oil temperature. At this moment, the
relationship indicating how the oil temperature threshold is
related to the initial oil temperature (FIG. 2) is used.
After the processings in S510, S514, and S518 have been performed,
the processings in S110 to S122 are repeatedly performed at
intervals of a sampling time.
Operation of the ECT-ECU 100 that is based on the structure and the
flowchart as mentioned above and that realizes the control device
for the automatic transmission in accordance with the fifth
embodiment will be described.
If a user of the vehicle turns the ignition switch on (NO in S100),
a determination concerning an abnormal state of each of the engine
coolant temperature sensor 300 and the engine intake air
temperature sensor 400 is made on the basis of a signal input
therefrom (S502).
If the engine coolant temperature sensor 300 is not abnormal (YES
in S504), an engine coolant temperature is detected and stored in
the memory as an initial coolant temperature, and an oil
temperature threshold is calculated on the basis of the initial
coolant temperature (S508, S510).
If the engine coolant temperature sensor 300 is abnormal (YES in
S504) and if the engine intake air temperature sensor 400 is not
abnormal (NO in S506), an engine intake air temperature is detected
and stored in the memory as an initial intake air temperature, and
an oil temperature threshold is calculated on the basis of the
initial intake air temperature (S512, S514).
If the engine coolant temperature sensor 300 is abnormal (YES in
S504) and if the engine intake air temperature sensor 400 is
abnormal (YES in S506), an AT hydraulic fluid temperature is
detected and stored in the memory as an initial oil temperature,
and an oil temperature threshold is calculated on the basis of the
initial oil temperature (S516, S518).
Thus, on the basis of states of the engine coolant temperature
sensor 300 and the engine intake air temperature sensor 400,
control for prohibiting a gear shift from fourth speed to fifth
speed is performed on the basis of an oil temperature threshold
that has been calculated on the basis of one of an engine coolant
temperature, an engine intake air temperature, and an AT hydraulic
fluid temperature.
As described above, according to the ECT-ECU that realizes the
control device for the automatic transmission in accordance with
the fifth embodiment, an oil temperature threshold is calculated on
the basis of one of an oil temperature detected by the oil
temperature detecting portion in the oil temperature detecting
step, a coolant temperature detected by the coolant temperature
detecting portion as coolant temperature detecting means in the
coolant temperature detecting step, the intake air temperature
detected by the intake air temperature detecting portion in the
intake air temperature detecting step when the engine is started.
If the coolant temperature detecting portion is abnormal, for
example, with the coolant temperature detected in the coolant
temperature detecting step being out of a measurable range, an oil
temperature threshold is calculated on the basis of an oil
temperature detected by the oil temperature detecting portion in
the oil temperature detecting step or the intake air temperature
detected by the intake air temperature detecting portion in the
intake air temperature detecting step. If the intake air
temperature detecting portion is abnormal, for example, with the
intake air temperature detected in the intake air temperature
detecting step being out of a measurable range, an oil temperature
threshold is calculated on the basis of an oil temperature detected
by the oil temperature detecting portion in the oil temperature
detecting step or a coolant temperature detected by the coolant
temperature detecting portion in the coolant temperature detecting
step. If the coolant temperature detecting portion is abnormal, for
example, with a coolant temperature detected in the coolant
temperature detecting step being out of the measurable range or if
the intake air temperature detecting portion is abnormal, for
example, with the intake air temperature detected in the intake air
temperature detecting step being out of the measurable range, an
oil temperature threshold is calculated on the basis of an oil
temperature detected by the oil temperature detecting portion in
the oil temperature detecting step. As described above, it is
possible to structure a backup system for contending with
abnormality of the detecting portions and the detecting steps.
According to the above-mentioned construction, if the coolant
temperature sensor is abnormal for example, an oil temperature
threshold is calculated on the basis of an oil temperature detected
by the oil temperature detecting portion in the oil temperature
detecting step or the intake air temperature detected by the intake
air temperature sensor. If the intake air temperature sensor is
abnormal, an oil temperature threshold is calculated on the basis
of an oil temperature detected by the oil temperature detecting
portion in the oil temperature detecting step or a coolant
temperature detected by the coolant temperature sensor. If the
coolant temperature sensor and the intake air temperature sensor
are abnormal, an oil temperature threshold is calculated on the
basis of an oil temperature detected by the oil temperature
detecting portion. As described above, it is possible to structure
a backup system for contending with abnormality of the sensors.
According to the above-mentioned construction, if the coolant
temperature sensor is abnormal, an oil temperature threshold is
calculated on the basis of an oil temperature detected by the oil
temperature detecting portion in the oil temperature detecting step
or the intake air temperature detected by the intake air
temperature sensor. If the intake air temperature sensor is
abnormal, an oil temperature threshold is calculated on the basis
of an oil temperature detected by the oil temperature detecting
portion in the oil temperature detecting step or a coolant
temperature detected by the coolant temperature sensor. If the
coolant temperature sensor and the intake air temperature sensor
are abnormal, an oil temperature threshold is calculated on the
basis of an oil temperature detected by the oil temperature
detecting portion in the oil temperature detecting step. Thus, it
is possible to structure a backup system for contending with
abnormality of the sensors.
[Sixth Embodiment]
As the AT hydraulic fluid temperature sensor 500 to which the
ECT-ECU 100 in accordance with the sixth embodiment is connected, a
first AT oil temperature sensor and a second AT oil temperature
sensor are provided. The first and second AT oil temperature
sensors may be disposed either at the same position or at different
positions. It is not absolutely required that the number of the
sensors be two.
The ECT-ECU 100 makes determination concerning an abnormal state of
each of the first and second AT oil temperature sensors on the
basis of signals input therefrom. For example, if a signal input to
the ECT-ECU 100 is out of a measurable range, it is determined that
a signal line extending from a corresponding one of the sensors has
been short-circuited or broken. If a signal input to the ECT-ECU
100 is within the measurable range but remains unchanged for a long
time, it is also determined that a corresponding one of the sensors
is abnormal. The ECT-ECU 100 selects a normal one of the sensors on
the basis of this determination and detects a temperature of
hydraulic fluid contained in the automatic transmission.
The system of the automatic transmission in accordance with the
sixth embodiment is identical in construction to the system in
accordance with the above-mentioned first embodiment, apart from
the number of the oil temperature sensors. Accordingly, a detailed
description thereof will not be repeated hereinafter.
A control structure of a program executed by the ECT-ECU 100 that
realizes the control device for the automatic transmission in
accordance with the sixth embodiment will be described with
reference to FIG. 11. In the flowchart shown in FIG. 11, flow
sequences identical to those in the above-mentioned flowchart shown
in FIG. 3 are denoted by the same step numbers. Accordingly,
detailed description thereof will not be repeated hereinafter.
In S602, the ECT-ECU 100 makes a determination concerning
abnormality of each of the first and second AT oil temperature
sensors on the basis of values input therefrom. In S604, the
ECT-ECU 100 determines whether or not the first AT oil temperature
sensor is abnormal. If the first AT oil temperature sensor is
abnormal (YES in S604), the operation is shifted to S606. If the
first AT oil temperature sensor is not abnormal (NO in S604), the
operation is shifted to S608.
In S606, the ECT-ECU 100 determines whether or not the second AT
oil temperature sensor is abnormal. If the second AT oil
temperature sensor is abnormal (YES in S606), the operation is
shifted to S612. If the second AT oil temperature sensor is not
abnormal (NO in S606), the operation is shifted to S610.
In S608, the ECT-ECU 100 stores an oil temperature detected by the
first AT oil temperature sensor in the memory as an initial oil
temperature. In S610, the ECT-ECU 100 stores an oil temperature
detected by the second AT oil temperature sensor in the memory as
an initial oil temperature.
In S612, the ECT-ECU 100 performs an error processing in the error
processing in S612, the ECT-ECU 100 issues a warning that is based
on the unmeasurability of a temperature of the oil contained in the
automatic transmission.
In S614, the ECT-ECU 100 calculates an oil temperature threshold on
the basis of an initial oil temperature detected by the first AT
oil temperature sensor or the second AT oil temperature sensor. At
this moment, the relationship indicating how the oil temperature
threshold is related to the initial oil temperature (FIG. 2) is
used. The flow sequences in S110 to S122 are thereafter performed
repeatedly at intervals of a sampling time.
Operation of the ECT-ECU 100 that is based on the structure and the
flowchart as mentioned above and that realizes the control device
for the automatic transmission in accordance with the sixth
embodiment will be described.
If a user of the vehicle turns the ignition switch on (YES in
S100), determination concerning an abnormal state of each of the
first and second AT oil temperature sensors is made on the basis of
values input therefrom (S602). If the first AT oil temperature
sensor is not abnormal (NO in S604), an oil temperature detected by
the first AT oil temperature sensor is stored in the memory as an
initial oil temperature (S608). If the first AT oil temperature
sensor is abnormal (YES in S604) and if the second AT oil
temperature sensor is not abnormal (No in S606), an oil temperature
detected by the second AT oil temperature sensor is stored in the
memory as an initial oil temperature (S610). If the first AT oil
temperature sensor is abnormal (YES in S604) and if the second AT
oil temperature sensor is abnormal (YES in S606), an error
processing is performed (S612).
Thus, an oil temperature threshold is calculated on the basis of
the initial oil temperature detected by the first AT oil
temperature sensor or the second AT oil temperature sensor (S614),
and control for prohibiting a gear shift from fourth speed to fifth
speed is performed on the basis of the calculated oil temperature
threshold (S110 to S122).
As described above, according to the ECT-ECU that realizes the
control device for the automatic transmission in accordance with
the sixth embodiment, two sensors for detecting a temperature of
hydraulic fluid contained in the automatic transmission are
provided, and an oil temperature detected by one of the sensors
that has turned out to be normal is detected as a hydraulic fluid
temperature. Thus, it is possible to structure a backup system for
contending with abnormality of the sensors.
According to the above-mentioned construction, two or more sensors
for detecting a hydraulic fluid temperature are provided, and an
oil temperature detected by one of the sensors that has turned out
to be normal is detected as a hydraulic fluid temperature. Thus, it
is possible to structure a backup system for contending with
abnormality of the sensors.
[Other Modification Examples]
The processings in S516 to S518 in the fifth embodiment shown in
FIG. 10 are not indispensable. It is appropriate to calculate an
engine stop time and to calculate an oil temperature threshold on
the basis of the engine stop time instead of performing the
processings in S516 to S518. It is also appropriate to calculate an
engine stop time and to calculate an oil temperature threshold on
the basis of the engine stop time in addition to performing the
processings in S516 to S518.
The embodiments disclosed herein are examples in all respects and
should not be construed in any limitative sense. The scope of the
invention is defined not by the foregoing description but by the
claims and is intended to cover all modifications that are
equivalent in significance and scope to the claims.
* * * * *